Hemopexin is a serum glycoprotein which binds the heme released by hemoglobin breakdown, transport it, and delivers it to the liver via specific receptors. Hemopexin consists of two domains, an N-terminal domain which binds heme, and a C-terminal domain which is essential for receptor binding. Since amino acid comparisons show that both domains are likely to have similar structures, this has enable us to model the heme binding domain. We have crystals of the intact molecule, but these prove to be extremely temperature-sensitive and very difficult to mount successfully in capillaries. Crystal freezing and the use of synchrotron radiation at SSRL will be the only way in which any useful data can be collected from these crystals.